Random pulse distribution indicator



DeC- 8 1964 H. MANN ETAL RANDOM PULSE DISTRIBUTION INDICATOR 3 Sheets-Sheet 1 Filed July l1, 1958 ATTok/VEV Dec. 8, 1964 H. MANN ETAL 3,160,740

RANDOM PULSE DISTRIBUTION INDICATOR Filed July 11. 1958 s sheets-sheet 2 [man Raser PuLsEs PuLsEs 2l FIG' 3 66 m a/NARY COUNTER 22 l lll/ L' gg W '55 l 160 /42 /6/ 147 mou T T T REAooz/r PuLsf L l GENE/wrok v 7U COUNTER PULSE AMPLIFIER GR/DS H. MANN WEZ/ORS A. E. RUP/DEL wiwi/ZM ATTORNEY Dec. -8, 1964 H. MANN ETAL 3,160,740 RANDOM PULSE DISTRIBUTION INDICATOR Filed July 11, '1958 s sheets-sheet s 55%?,- v FIG. 4 m Clegg?? TRAJSOLATQR H. MANN Nm/T0 A. E. RUPPEL MKM ATTORNEY United States Patent Utilice Patented Dec. 8, 1964 mimi/lil RANDM PULSE DESFRIBUTN liNDlCATR Henry Mann, llerkeley Heights, NJ., and Alfred E. Rappel, East Rockaway, nssignors to Bell hele phone Laboratories, incorporated, New York, FLY., a corporation New Yori:

Filed Iinly il, i953, -er. No. 7127,?{75 l Claims. (El. 235-91Z) This invention relates to a pulse distribution indicator. More particularly, the invention relates to a device for counting pulses which occur during time intervals of controllable duration and for classifying the interval pulse counts according to the magnitudes thereof.

The invention will be described in connection with its application to a high speed data transmission system. However, it will be apparent that the usefulness thereof is not limited to such an application.

ln a high speed data transmission system telegraphie mark and space signals are utilized to transmit inforrnation by means of electrical impulses traveling through a suitable transmission medium. In one system, the mark and space signals, or information bits, are transmitted at a rate which is of the order of magnitude of 1500 bits per second. This is considerably faster than the transmission rate in a conventional telegraphic transmission system in which information is transmitted at the rate of approximately 100 bits per second. Ordinary tele* graph metallic transmission media are capable of transmitting only a relatively narrow band of frequencies so they are unsuitable for the transmission of the relatively broad band of frequencies required for the rapid Signal variations in a high speed data transmission system. Therefore, radio, or selected and treated telephone message channels, must be utilized in order that the transmission medium may have suitable transmission characteristics to accommodate the relatively high speed signal variations. Conventional telephone message channels must be selected and treated to reduce the elfects of noise and distortion that would be of no consequence to telephone message transmission or to ordinary telegraph transmissions, but which would introduce errors in a high speed data system.

ln the prior art there are devices for determining the long time average error rate by detecting and counting the number of errors in a received data signal. However, it is often advantageous to have information which reveals the short time error distribution, i.e., information relating to the probability of the occurrence of a predetermined number of errors in short time intervals of different durations. This type of information is important to the evaluation of various error checking codes and parity systems. As an example of the utility of data indicating the short time distribution of errors, assume that a high speed data transmission system will use a simple parity checking code and that the data word lengths to be transmitted will be about bits. If the short time distribution of errors indicates that there is a high likelihood of having multiple errors in ZO-bit intervals, it is then likely that the simple parity checking code will fail to detect errors in a large number of cases. Therefore, it will be necessary to take some remedial steps such as changing the word length, adopting a different parity checking,T code, or perhaps treating the system to reduce noise and distortion.

Accordingly, it is one object of the invention to deter mine the distribution of pulses in time intervals of pre determined duration in a pulse train in which pulses may occur at random.

A further object is to measure the short time distribution of errors in a high speed data transmission system.

Another object is to count separately the number of time `intervals during which predetermined numbers of pulses occur.

A more specific object of the invention is to determine in a data transmission system the number of intervals of predetermined duration in which more than one error occurs and to determine the specific distribution of such errors, ie. the specific number of intervals containing specific numbers of errors.

A further specific object is to determine in a data transmission system the number of intervals containing errors in consecutive data bit periods and to determine the specific distribution of such errors, i.e. the specific numbers of intervals containing specific numbers of consecutive errors.

These and other objects of the invention are realized in an illustrative embodiment thereof in which a first random pulse initiates the examination of a time interval of predetermined duration which includes the initial r-andom pulse. Binary counters total the random pulses occurring during each interval. A circuit, which is actuated by the initial random pulse in each interval, generates a readout pulse at the end of the interval to cause the binary count to be translated into a decimal count and stored in an appropriate decimal register. The readout pulse also actuates a circuit for resetting the binary counters to Zero. Additional circuits may be provided for initiating early readout after n random pulses have been counted in any one interval and, if desired, to initiate early readout at the end of a group of consecutive random pulses in any one interval.

A better understanding of the invention may be obtained from a consideration of the following description thereof in connection with the attached drawing in which:

Fifi. l is a simplied block and line diagram illustrating the invention;

FG. 2 is a block and line diagram of an illustrative embodiment of the invention;

FlG. 3 is a schematic diagram of a representative portion of the binary counting circuits and of the translator of FIG. 2;

FIG. 4 is a schematic diagram of the timing portions of the counting interval controlling circuits of FIGS. l and 2; and

FIG. 5 is a schematic diagram of the consecutive pulse responsive portions of the counting interval control circuits.

Referring to FIG. 1, a source 10 supplies to pulse counter 11 a pulse train in which the pulses may occur at random. A counting interval controller 12 is responsive to a rst random pulse for controlling the duration of the interval during which the random pulses are counted. At the end of such interval a readout pulse is applied from controller l2 to an interval count sepan,k rator i3 which is responsive to the magnitude of the s Upon the completion of 'an interval during which a single random pulse occurred, interval count separator l5 actuates the decimal register l thereby indicating the y occurrence of an event comprising an interval containing n a single random pulse. if an interval includes two random pulses, separator 13 actuates decimal register II to indicate tne occurrence of an event which includes two random pulses. Events which include n random pulses would cause separator 13 to actuate decimal register n. After a predetermined measuring period has elapsed, decimal registers I through n indicate the numbers of intervals, or events, during that period which included l through fz random pulses, respectively. For example, if at the time of reading, registers I, II n indicate 9, 4 2, it is then known that during the measuring period there were nine intervals of predetermined length containing one error, four intervals containing two errors, and two intervals containing n errors. It will be bserved from the subsequent description of the invention that interval count separator 13 actuates one only of the decimal registers in the bank 16 in response to each event.

Referring to FIG. 2, the source of random pulses is an error detector 17 which might be, for example, a matching and error counting circuit or a parity checking circuit in a high speed data transmission system (not shown). Pulses from error detector 17 are coupled via an error pulse amplifier 1S to the input of a further error pulse amplifier 19 and to the input of a cathode follower 20. Negative-going output pulses from amplifier 19 are applied to one input of a binary counter 21. Counter 21 is connected in cascade with two further binary counters 22 and 23 for counting error pulses in a bniary counting system. Any number x of counters may be employed as may be necessary for the particular system under study, but three counters are utilized here for the purposes of illustraton.

The outputs of each of the binary counters 21, 22, and 23 are coupled to a binary-to-decimal translator 26 via cathode follower circuits 27, 28, and 29. Translator 26 corresponds to the interval count separator 13 of FIG. l, for it is in translator 26 that the binary count in counters 21 through 23 is translated into a decimal count and applied to an appropriate one of the decimal registers I through V in the decimal register bank 16 via counter pulse amplifiers 3l) through 34, respectively. In this case, the number n, hereinbefore mentioned in connection with FIG. 1, is equal to five. Although three binary counters and five decimal registers are indicated in FIG. 2, it is understood, of course, that either more or less of these components could be utilized as may be necessary. The details of the counting and translating circuits will be hereinafter described in connection with FIG. 3.

The control of the duration of the intervals during which error pulses are counted is accomplished by circuits which are responsive to a first error pulse in the output of cathode follower 2f?. One output of cathode follower is utilized to trigger counting interval gate startpulse generator 37 wherein a sharp impulse is generated for actuating counting interval gate 3d.

Gate 38 generates a rectangular output pulse of precise duration which is applied to a readout pulse generator 39 wherein a readout pulse is produced in response to the trailing edge of the rectangular pulse. The output of gate 3S is also coupled back to the input of start-pulse generator 37 via an error pulse suppressor dil. Suppressor 4t) prevents the retriggering of start-pulse generator 37 in response to error pulses from cathode follower 2t) for the duration of the rectangular output pulse from gate 38. The details of the arrangement and operation of counting interval gate 3S and its associated circuits will be hereinafter described in greater detail in connection with FIG. 4.

Readout pulses in the output of generator 39 are applied to translator 26 via lead 136 to initiate the readout therefrom to the bank 16 of decimal registers as will be hereinafter described in connection with FIG. 3. Readout pulses in the output of generator 3g are also applied to a counter reset pulse generator 41 which is responsive thereto for resetting binary counters 21 through 23 to the zero count condition. Generator 41 may comprise, for example, a monostable multivibrator having the output thereof differentiated so that the differentiated trailing edge of the multivibrator output wave may be utilized to reset counters 221 through 23 after the readout operation from translator 26 has been completed and before the end of the next succeeding bit interval.

A counter manual reset switch d2 is also indicated in FIG. 2 and may comprise, for example, any suitable bias source and switching means for manually applying a bias to counters 21 through 23 to reset them to a predetermined counting condition.

Translator 2d also includes a fifth error detecting circuit, as will be hereinafter described in connection with FIG. 3, for actuating a gate reset pulse amplifier 033 to trigger gate 3S back to its normal inactive condition before the expiration of the timed interval in response to the occurrence of the fifth error pulse in a given counting interval. This arrangement is necessary since only five registers are provided in FIG. 2 and it is therefore necessary to initiate readout and stop the action of binary counters 21 through 23 even though more errors might occur during the interval if it were permitted to continue for its natural timed duration. In the particular system with which the pulse distribution indicator of FIG. 2 is used, information which includes five or more errors in a given word interval is discarded. Therefore, for such a system it is only necessary to indicate separately those events having up to ve errors per interval.

If it is desired to determine the distribution of errors occurring during consecutive bit intervals, as distinguished from errors which occur at any time during a counting interval, the mode of operation of the circuit of FIG. 2 may be modified. A single-pole-doublethrow switch #i6 is provided for connecting into the counting interval controlling circuits means for producing an output pulse in response to the occurrence of a bit interval which does not include an error following consecutively a bit interval which does include an error. Switch 46 includes an armature 47 and two contacts 45 and 49. When the pulse distribution indicator is operating in the interval timing mode, armature d'7 contacts the grounded contact i3 as illustrated. When the indicator is to be converted to the consecutive error mode of operation, armature 47 is moved to Contact 49 for coupling output pulses from cathode follower 2@ to a consecutive error detector circuit 5ft.

The output of detector Sti is coupled to a consecutive error reset pulse generator 51 to produce an output pulse in response to the occurrence of a good bit interval following an eroneous bit interval, i.e., the termination of a series of consecutive pulses. The output of reset pulse generator 51 is applied to the input of reset pulse amplifier 43 to initiate an early readout, before the end of a normal timed counting interval, in the same manner hereinbefore described in connection with the actuation of amplifier 13 in response to the fifth error detecting circuit of translator 26.

summarizing the operation of the pulse distribution indicator illustrated in PIG. 2, error pulses from detector 17 are applied via error pulse amplifiers 13 and 19 to the binary counters 21 through Z3. The error pulses are also applied via Vcathode follower 2u to start pulse generator 37 to initiate the timing of a counting interval of a predetermined duration which includes the initial error pulse. At the end of the counting interval, gate 3S causes an impulse to be produced by generator 39 as a readout pulse. The readout pulse is applied to translator 26 to cause an appropriate one of the decimal registers in the register bank 16 to be actuated for storing in a decimal counting system the total number of counting intervals during which the same number of error pulses occurred. The readout pulse from generator 39 also actuates generator i1 to cause the counters to be reset after the read out operation has been completed. The counting interval may be terminated upon the occurrence of the fifth error in any given interval by a pulse which is applied to gate 33 amonio from the gate reset pulse amplilier 43. After a counting interval has been terminated the indicator remains inactive until a subsequent error pulse is detected by error detector 17.

lf it is desired to count only the consecutive errors, armature 47 is operated into engagement with contact 49 to connect the consecutive error circuitry into the counting interval controlling circuits for terminating a counting interval upon the occurrence of an erroneous bit interval followed by a good bit interval. In this mode of operation, if registers l through V in bank 16 indicate 8, 9, 10, 7, 2, respectively, it is known that during the measuring period there were eight intervals comprising a single error, nine intervals comprising two consecutive errors, ten intervals comprising three consecutive errors, seven intervals comprising four consecutive errors, and two intervals comprising tive consecutive errors. All of the previously described circuits of the indicator are operative and any given interval may be terminatedtl) by the expiration ofthe predetermined counting interval as measured by gate El@ if such interval were no longer than the transmission time of live data bits, (2) by the occurrence of the fifth consecutive error in the interval as detected by the fifth error detector in translator 2d, or (3) by the occurrence of an erroneous bit interval followed by a good bit interval as indicated by detector Sti and generator 51. ln this mode of operation, single isolated error pulses could cause decimal register l to be actuated for indicating the occurrence of an event in which a single error has occurred. However, the arrangement of translator 26 may be readily modified, as will be evident from the description thereof in connection with FIG. 3, to actuate registers only in response to the occurrence of events which include more than one erroneous data bit.

Referring to FlG. 3, there are illustrated the details of binary counter Z1 together with the cathode follower circuit 27 and translator 2d. Counters 22 and 23 and cathode followers 28 and 29 (none of which are illustrated in FlG. 3) are similar to counter 2l and cathode follower 27, respectively, and are connected to translator Zo in a similar manner as will be hereinafter discussed. Binary counter 2l is a bistable multivibrator which includes two triode discharge devices 52a and 52h. rhe anodes 53 and 56 thereof, respectively, are cross-coupled to the control grids 57 and Sti via the cross coupling time constant circuits 59 and et?, respectively.

Error pulses from the output of error pulse amplifier l@ are applied via lead 63 to the multiple-connected cathodes of a pair of diodes dll and 62 which have the anodes thereof connected to anodes 53 and Se, respectively. With this input connection arrangement the negative-going error pulses are coupled to the control grid of the conducting triode via the diode which is connected to the anode of the nonconducting triode. Each negative-going error pulse, therefore, causes the multivibrator to he transferred from one stable conducting condition to the other in a well known manner. Thus, the binary counter 21 is transferred back and forth between its One and Zero conditions by the negative-going error pulses which are ap'- plied thereto from error pulse amplifier 19 via the lead d3.

rl`he output voltage variations at anode Eiare coupled via lead de to the next succeeding binary counter, counter 22. Thus the negative-going transitions at anode 53 cause binary counter 22 to be actuated back and forth between its @ne and its Zero conditions, and in a similar mannerl the negative-going transitions at one anode of binary counter 222 are coupled to binary counter 23 to actuate counter 23 back and forth between its One and Zero conditions.

A neon bulb d'7 is connected in series with a resistor d between the positive 'terminal of battery 69 and anode ils of counter 2l. Since battery 59 supplies operating potential to anode Sti, the bulb e7 is arranged to have suflicient potential difference impressed thereon when triode 522i: is conducting to tire bulb 67. Thus, the bulbs o7 ti associated with each of the counters are lighted to provide a visual indication of the binary Zero condition of their respective counters.

Negative-going reset pulses are applied to control grid 57 of device 52h in each of the counters via a diode 7i) for resetting all of the counters to the Zero binary condition, i.e. the zero count condition.

Voltage variations at anodes 53 and 56 are coupled to the control grids '71 and 72 of discharge triodes 73 and 76, respectively, in cathode follower 27. Anode load resistor le comprises with thev series-connected resistors 77 and 73 a potential divider for controlling the potential at control grid 7l in response to the conducting condition of device 52a. Similarly, anode resistor 55 comprises with series-connected resistors 79 and 8i) a potential divider for controlling the potential of control grid 72 in response to voltage variations at anode da. Gperating potential for triodes 73 and 76 is supplied from the positive terminal of battery 69 to anodes S1 and S2, respectively. Cathodes 33 and 86 are connected to the grounded negative terminal of battery di? by the series-connected resistor combinations of resistors 87 and @3, and 39 and 90. Triodos 73 and 7d are normally conducting with the amount of conduction in each thereof controlled by the conducting condition of triodes 52u and 5211, respectively.

The output of cathode follower 27 is derived from a terminal 91 which is common to resistors S9 and 9) and a terminal 92 which is common to resistors 87 and S8. This output is coupled to the circuits of translator 2.6. Thus, cathode follower Z7 comprises two cathode follower circuits. ln general terms, the outputs of the x binary counters are coupled to translator 26 by means of 2x cathode followers.

Translator 26 comprises tive `three-diode coincidence gates 96 through lili) which are arranged to control the operation of registers I through V, respectively. lf binary counters 2l, 22, and 23 are in their binary One, Zero, and Zero conditions, respectively, at the end of a counting interval, a pulse count of one in the decimal counting system is indicated. The counter output voltages bias gate 95 into coincidence, and register l is actuated in the manner hereinafter described.

The number of gates utilized is equal to the number n of registers that are employed. Each of the gates 96 through 1li-tl includes three diodes a, b, and c. Cathode follower output terminal 91 is connected in multiple to the cathodes of diodes a in gates $7 and 99. Cathode follower output terminal 92 is connected to the cathodes of diodes a in gates 9d, 98, and ltltl. The cathodes of the diodes b and c in each gate are connected to the output terminals of the cathode followers 2S and 29 in a similar The latter connections are not shown in FlG. 3 since they are similar to the connections that are shown andrwould only serve to complicate the drawing unnecessarily. The result of this connection arrangement is that each of the gates 96 Ithrough 106 is biased into its coincidence condition by the cathode follower output voltages in response to a ditferent binary condition of the counters 2l through 23. Thus, gate 9d would be the only gate in coincidence in response to the binary count for one error pulse. Gate i7 would be the only gate in coincidence for the binary counter condition indicating two error pulses, and gate tilt? is the only gate that would be in coincidence for the binary counter condition indicating tive error pulses. The anodes of all diodes in each gate are connected in multiple. Thus, each gate has three, or n, input terminals which are the cathodes of the diodes thereof and one output terminal which is the multiple-connected anode connection thereof.

The multiple-connected anodes of gates 96 through lill) are connected, respectively, to the cathodes of voltagel amplitude selecting diodes `lill through 195. The ano-des of diodes lill through los' are connected in multiple to a first intermediate voltage bus ldd. The potential of bus lt is established by the connectionthereof to an intermediate point on a potential divider comprising the resistors 169 and lllll which are connected in series between the terminals of a battery lll. The potential of bus 163 may be further stabilized by the connection of a voltage regulator tube M2 between bus ldd and the grounded negative terminal of battery lll. The potential of bus 10S may thus be established at some level such as, for example, 75 volts with respect to ground.

The multiple-connected anodes of gates 96 through ltlll are also connected to the positive terminal of a battery 113 via resistors alle through lili?, respectively. The multiple-connected anodes of gates to through lull are further connected, respectively, to the anodes of voltage amplitude selecting diodes 121 through i125 and to the anodes of voltage amplitude selecting diodes 123 through 132. The cathodes of diodes lll through 125 are connected in multiple to the output of readout pulse generator 39 via a lead 136. The potential of lead 136, with respect to ground, may vary, for example, between +60 volts in the absence of a readout pulse and +200 volts during a readout pulse. Thus, it will be seen that in the absence of a readout pulse, diodes Hl through 25 are biased into conduction with a small component of current flowing therethrough from battery ll via the resistors lilo through l2@ and with another component of current owing therethrough from bus lua via diodes ltlll through 105.

Any one of the gates 96 through lull which is in the noncoincidence condition provides a voltage sink for bus 163 via the corresponding one of diodes lill through lit' and the potential at the multiple-connected anodes or" such gate remains at approximately the potential of bus 16S. In a similar manner diodes lZl-l provide voltage sinks for bus MPS in the absence of a readout pulse.

Five potential dividers comprising the resistors 13'7- 138, lSQ-ldil, tel-142, ldd-M7, and 14S-'M9 are connected in shunt with one another between the terminals of a battery iSd. These potential dividers are arranged so that the intermediate terminals ll through 155 there on are all at a second intermediate voltage which may be, for example, approximately +9() volts with respect to ground. The cathodes of diodes T128 through E32 are connectcd to terminals lSl through 155, respectively, and the same cathodes are also connected to the inputs of counter pulse amplifiers 3d through 34 Via coupling capacitors 158 through lie, respectively.

A further three-diode coincidence gate loe comprising diodes a, b, and c is bridged across gate ltltl and comprises the fifth error detector circuit hereinbefore mentioned. The cathodes of diodes a, b, and c in gate i166 are connected respectively to the cathodes of diodes a, b, and c in gate lilil. The anodes of the diodes in gate lod are connected in multiple to the positive terminal of battery 113 via a resistor la7 and to the cathode of a voltage arnplitude selecting diode d68 which has the anode thereof connected to bus ldd. A lead l@ connects the multipleconnected anodes of gate 166 to the input of reset pulse amplifier e3.

Considering now the operation of the counting and translating circuits of FIG. 3, the counter multivibrator rests initially in its Zero condition with triode 52a conducting and triode 52h Oil prior to the application of error pulses thereto. With triodc 52E] in its nonconducting condition there is insuilicient potential drop across its load resistor S5 to bias neon bulb 67 into conduction. In this condition anode 53 is at a lower potential than anode 56; and accordingly, in cathode follower 27, triode 76 is conducting more heavily than triode '73. Cathode Follower output terminal 91 is at a higher potential with respect to ground than output terminal 92.

The resistors 87 through 9'@ in cathode follower 27 are so designed with respect to the condition levels in triodes 73 and 76 that the relatively high potential at terminal ll is suilicient to block the diodes a in gates 97 and 99. The relatively lower potential at terminal 92 is insuiilcient to block diodes a of gates 96, 98, and ldd. The remaining diodes in gates 96 through lill) are biased in a similar manner from the output connections of cathode followers 28 and 29 -so that at least one diode in each gate circuit is conducting prior to the application of a rst error pulse to binary counter 2l, and each gate is in its noncoincidence condition. As has been hercinbefore noted, diodes lill through ltl and diodes lll through are all conducting. Diodes "i128 through l32 are all blocked since their cathodes are all at the second intermediate voltage, 90 volts with respect to ground, and their cathodes are all at the rst intermediate voltage, the 75-volt potential of bus lill; when diodes lill through are conducting.

The first error pulse which is applied to counter 2l Via lead 65 triggers the multivibrator by coupling a negative pulse to grid 53 via diode e2 and cross coupling circuit 56. This pulse biases triode 52a Gif thereby transferring conduction to triode 52h in a Well known manner. The additional current drawn through load resistor 55 by triode 521; increases the potential drop thereacross by an amount which is sufficient to re neon bulb 67. The transfer of conduction between triodes in counter 2l shifts the conduction levels in cathode follower 27 so that output terminal 92 is now at a relatively higher potential than is output terminal Sel thereby blocking diodes a in gates 96, 93, and The potential at output terminal 9i is now at the relatively low level and unblocks diodes a in gates 97 and 99.

The blocking of diode a in gate 96 puts gate 96 in co incidence, and one of the voltage sinks which is available to bus lit. is removed. However, the voltage sink which is represented by diode lZl is still available and no output pulse is coupled to counter pulse ampliiier 2i@ via diode 123 and capacitor 158. If a readout pulse is applied t0 lead i3d prior to the occurrence of a second error pulse, diodes llZl through i225 are all blocked, thereby removing both Voltage sinks which are available to bus M8 via diode lill. The potential at the anode of diode i128 begins to rise thereby blocking diode lill, and current begins to llow from battery ll?) through resistor llld, diode lZll, and resistor llSS to ground. As the low of current through resistor 138 increases, the potential of terminal lSll increases and a positive pulse is coupled via capacitor 15S to counter pulse amplifier 3i) to actuate decimal register l.

if a readout pulse has not occurred prior to a second error pulse, that second error pulse triggers counter 2l once more thereby biasing triode 52a into conduction and coupling a negative-going voltage transition via lead 66 to trigger counter 22. The operation of the counters and cathode followers continues in response to each error pulse in a manner similar to that hereinbeforc described. The second error pulse causes the coincidence condition to be shifted from gate 96 to gate 97 and each subsequent error pulse causes the coincidence condition to be shifted to the next succeeding gate. The application of a readout pulse to lead lli-6 at any stage in this operation causes the one of the diodes 128 through 132 which is associated with the gate in coincidence to be biased into conduction thereby coupling an output pulse to the associated counter pulse amplifier for actuating a corresponding decimal register.

lf gate lldtl is biased into coincidence prior to the application of a readout pulse to lead 136, gate 166 is also biased into coincidence. Since gate 166 is not connected to lead lilo it provides the only Voltage sink for bus M33 via diode lld. Accordingly, With gate ldd in coincidence, the potential of the multiple-connected anodes thereof and the potential of lead l@ begin to rise as a result ofthe connection thereto of battery M3 via resistor 167. This increase in potential comprises a positive-going output pulse which is coupled via lead le@ to the gate reset pulse amplifier of FIG. 2. The triggering of amplifier d3 in response to the pulse on lead lo@ causes gate 38 to be actuated to terminate the counting interval and cause a readout pulse to be generated before the expiration of the timed duration of the counting interval. The readout pulse appears on lead 13d and blocks diodes 121 through Since gate lll@ is in coincidence and diode 125 is locked by the readout pulse, the potential at the anode of diode 132 increases as a result of the connection thereof to battery 113 via resistor Mtl. The increase in potential biases diode 132 into conduction thereby producing a positive-going pulse at terminal 15'5, which pulse is coupled to counter pulse amplifier 34- and decimal register V via capacitor 62. The actuation of register V indicates the occurrence of an event in which tive errors occur ed during the counting interval.

Summarizing the operation of the counting and translating circuits of FiG. l, which are partially illustrated in schematic form in FIG. 3, error pulses are counted in a binary counting system by counters 2l through 23. Each counter has two outputs of opposite phase with respect to one another as is well known for bistable multivibrators.

Each output then comprises a binary signal voltage wave, and the combined binary conditions of such waves at any one time comprises the binary code representation of the number of error pulses counted up to that time. Each successive count which is indicated by counters 2l through 23 biases a different one of the coincidence gates Se through lull in FlG. 3 into coincidence with all three diodes of such gate being blocked. The application of a readout pulse to lead l5@ causes the one of the diodes 123 through lSZ, which is associated with the one gate in coincidence, to be biased ON thereby producing an output pulse which is coupled to the corresponding counter pulse amplifier to actuate the corresponding Vdecimal register. ln this manner the binary counts in counters 21 through 23 are converted to decimal counts, and the decimal counts are stored in decimal registers l through V by actuating those registers to total separately the nurnbers of counting intervals during which different numbers ot' error pulses occurred. Stated in another way, the binary counts of the number of error pulses which occur during each one of a series of successive counting intervals are separated, or classilied, according to the magnitude of the count and stored in separate count storing means.

Referring to llG. 4, the timing portion olf counting interval controller l2 is illustrated in detail together with the detail of readout pulse generator 39. Start pulse generator 57 comprises a pair of discharge triodes ltla and lille connected as a monostable multivibrator with positive grid return. The anodes 17E and 172 are connected to the positive terminal of a battery 173 by means oi load resistors li'o and 1.77, respectively. rthe normal bias on thecontroi grid 178 is established by the connection thereof to an intermediate terminal 179 on a potential divider which comprises the resistors itil) and lill connected in series between the terminals of battery ll'l. Control grid ILSE is connected to the positive terminal of battery U3 via resistor 133. Cathodes 136 and lt are connected together and both cathodesare connected to the grounded negative terminal of battery 173 via the common cathode resistor 158.

Anode l'l is cross-coupled to control grid 1?2 by capacitor 'The output of generator 37 is coupled from anode 1.72 to the input of counting interval gate 38 by .leans of a capacitor 190 which `is connected in series with a pair of diodes lill and 192. The time constant of the cross-coupling capacitor lli) and positive grid return resistor 133- is very short, and the multivibrator is in its unstable condition for a very snort time. Start pulse generator 37 produces a positive-going output pulse of short duration in response to each error pulse which is applied to control grid 78.

Counting intervalgate 3S comprises two discharge trio-es lvtln and ob which are also arranged yas a monostable multivibrator. M7 which is connected to the positive terminal of battery llli via a load resistor i538, a cathode 199 which is connected to ground via a resistor' 2M?, and a control grid Edi which has the normal operating potential thereof Triode @da comprises an anodeA established by a potential divider which includes resistors 232 and 203 connected in series between the terminals of battery l'73. Triode l'llb comprises an anode 2il4 which is connected to the positive terminal of battery 173 via load resistor 2%, a control grid Zilli which is cross coupled to anode via capaictor 2li?, and a cathode 2% which is connected directly to cathode 199. Control grid 2% is returned to ground by means of a seriesconnected resistance combination comprising resistor 269, rheostat Zlil, and cathode resistor 200. The time constant of capacitor 2li? and the above-mentioned seriesconnected resistance combina-tion is relatively long so that counting interval gate 38 remains in its unstable condition after the triggering thereof for a predetermined number of bit intervals which comprise the predetermined counting interval. The pulse distribution indicator which is illustrated in FlG. 2 with live decimal registers may have a counting interval of about iiteen to twenty bit intervals. The duration of the counting interval may be regulated by adjusting rheostat 2li) to change the duty cycle of gate 3S. Rheostat 2li? is part of the Ori-time charging current path ior'the capacity 297 which cross-couples anode l?? to control grid 235, and the adjustment o rheostat 2lb changes the time constant of the Ott-tinte cross-coupling circuit of gate 3S.

input pulses to counting interval gate 3S are coupled to control grid Zell from generator 37 via capacitor 191') and the diodes lill and l92. Diodes 191 and l92 are included in the coupling circuit to prevent negative-going voltage transitions at anode l from affecting the operation of gate 38. A lead T195 is also connected to control grid lll for applying reset pulses thereto from gate reset pulse amplier d3. The output of gate 38 is coupled from anode Zilfi to the readout pulse generator 39 by means of a coupling capacitor 2li and a grid current limiting resistor M2..

A diode discharger is provided for capacitor 207 to facilitate the rapid restoration of the charge thereon to its normal level following the transfer of gate 38 from its unstable toits stable condition at the end of a counting interval. The diode discharger comprises a diode-connected triode 2 l3 having the anode 2id thereof connected to control grid 2do. Triode 2l3 is also provided with a control grid 2lb' and a cathode Ello which are connected to an intermediate terminal 217 on a potential divider comprising resistors 2l?, and 2l9 connected in series between the terminals of battery 173. An alternating current by-pass capacitor 22d is connected inparallel with resistorl to by-pass transient Voltage variations so that the bias condi-tion of cathode 2id will not be seriously atlected by transient voltages at anode M7. Potential divider 2lb-219 is designed so that when gate Sie is in its stable conducting condition cathode 2l6 is at a slightly lower potential than anode Zll. Thus, triode 12l3 is normally conducting when gate is in its stable condition.

Since error pulses will occur during the counting interval when gate 3b is in its unstable condition, it is necessary to prevent the application ol such pulses to control grid Zbl. input pulses applied to grid Ztll while gate 3 5 is in its unstable condition affect the conduction level of triode @da and thereby change the charge on capacitor 267. Such changes in tl e charge on capacitor 267 will of course aiiiect the timing of the output pulse from gate 3S in a well known manner. Accordingly, error pulse suppressor is provided to suppress error pulses at control grid l while gate 3S is in its unstable condition. lulse suppressor comprises a triode 221 having the anode 222 thereof connected to control grid 17S via a resistor 223. Cathode 2255 is connected directly to ground, and control grid 229 is connected Via resistor 23@ to a terminal 2M on a potential divider comprising resistors 232 and 2.33 connected in series between anode Zilli and thenegative terminal'oi a battery 23E. The positive terminal of battery 23d is connected to ground.

The resistance of resistor is made much smaller assenso 13 'setting generator 51 in its second table conduction condition.

The output of generator l is coupled from anode 271 thereof via capacitor 287 and a resistor 28S to a control grid 289 of triode 290 in the reset pulse ampliiier 43. Cathode Zijl or" triode 296 is connected directly to ground and the anode 292 of triode 231i) is connected to counting interval gate 33 by means of lead 195. Anode potential for triode 2% is supplied via lead 195 and resistor 2M in FIG. 4. The bias potential of grid 259 is established by means of a potential divider which includes the resistors 293 and 296 connected in series between the terminals of battery 256 and having an intermedite terminal 297 thereon connected to control grid l via resistor 23S and a resistor 29S. An alternating current by-pass capacitor 299 is connected between terminal 297 and ground. rIriode 2% is normally biased Off by the potential divider 293-296 in the absence of a positive-going pulse on grid 239. Capacitor 2.87 and resistor 29S cornprise a differentiating circuit for differentiating the negative-going output pulses from anode 127i in generator itl. The leading edge of the negative-going rectangular pulse from generator 51 produces no change in the conducting condition of triode Zitti which is normally non-conducting. However, the positive-going trailing edge thereof produces a positive impulse on grid 28? which results in a negative-going voltage pulse, the reset pulse, at anode 292.

Another source of input signals for reset pulse amplifier i3 is provided by connections to control grid 289 from translator 26. A potential divider comprising the resistors 366 and 3M and a common terminal 3h22 therefor is connected in series between the terminals of battery 250. Voltage signals from the fth word detector gate 166 in translator 26 in FIG. 3 are applied to control grid 239 via a diode 363, terminal 3M, a coupling capacitor 306, diode 307, and resistor 23S connected in series therebetween in the order named. A resistor Seil is connected between ground and a terminal 399 which is common to diode 307" and capacitor 3de.

Diode 3&3 and the potential divider Still-301 isolate ampliiier t3 from translator 26. The voltage signals applied to diode 363 comprise positive-going rectangular pulses having a duration which corresponds to the time interval which elapses between the time that gate 166 in translator 26 is biased into coincidence and the time that counter reset pulse generator 41 causes binary counters 21 through 23 to be reset to the Zero condition thereby restoring gate ld to the noncoincidence condition. The last-mentioned positive-going rectangular pulse is difierentiated by capacitor 366 and resistor 368, and the positive-going impulse resulting from the differentiation of the leading edge thereof is applied via diode 3G37 and resistor 2.88 to control grid 239 to initiate the generation of the reset pulse as hereinbefore described. The application of the negative-going pulse which results from the differentiation of the trailing edge of the rectangular pulse from gate los is blocked by diode 307 and does not reach amplier 43.

The operation of the consecutive error circuitry is initiated by setting armature 47 or" switch 46 in contacting engagement with Contact 49 as illustrated. Triode 25d-6 is normally biased Oli by potential divider 257-2S8, and capacitor 247 is charged to a potential which is equal to the terminal voltage of battery 250. Generator 51 rests in its tirst stable condition with triode 266s conducting and triode 266b nonconducting. Triode 29@ of reset amplifier 43 is based Oli as hereinbefore noted.

Error pulses from cathode follower 29 are now coupled to control grid 253 via armature 47, capacitor 263, and resistor 261. Each error pulse is of sutlicient magnitude to bias triode 246 into conduction thereby providing a low impedance discharge path for capacitor 247. Capacitor 247 discharges to ground potential through triode 24,6 during the brief conduction interval thereof. Upon the termination of each pair of pulse,

triode 24d returns to its nonconducting condition and capacitor 247 charges via resistor 25 and rheostat 252 toward the terminal voltage of battery 25d. The time constant of this charging path may be regulated by adjustment of rheostat 252 and should be set so that capacitor 247 will be restored very nearly to its quiescent charge within approximately 1% bit intervals.

The drop in potential at anode 243 upon the triggering of triode 246 is coupled to control grid 2do in generator 5l via lead 253 to bias triode Edda @ff and trigger generator 5l into its second stable conducting condition with triode 266i; conducting. Upon the triggering of triode 266g Off, the increase in potential at anode 27d is coupled to control grid 7e for biasing triode Zeeb into conduction thereby initiating a negative-going voltage pulse at anode 271 in a well known manner. In addition, the potential drop across resistor 269, as a result o the current flowing in triode 26st?, also tends to bias triode 266g Off.

Upon the occurrence of a second consecutive error pulse, triode 24,6 is once more triggered into conduction thereby discharging capacitor 247 and dropping the potential of control grid 2de back to ground potential. This operation takes place before the charge on capacitor '-i has risen sufficiently to bias triode Za On and is illustrated by the waveform adjacent lead 283. The operation continues until a bit interval with no error pulse occurs. Thus, capacitor 247 and triode 246 co-operate to detect the occurrence of consecutive error pulses and to hold generator 5l in its second stable conducting condition for the duration of a consecutive error pulse train.k When a bit interval with no error pulse occurs, capacitorL charges to its maximum potential thereby increasing the potential on grid 235 sufficiently to cause conduction in triode 26541. Generator S3. is restored to its first stable condition, and the negative-going output pulse at anode 271 is terminated. Thus, the total duration of the outputk pulse from generator 5l is substantially the same as the duration of the consecutive error pulse train. g The termination of the negative-going pulse causes a positivegoing impulse to be applied to control grid 289 of reset pulse ampliiier 43 as hereinbefore described thereby applying a reset pulse via lead 7.95 to gate 38.

Error detector 5d and generator 51 are not affected by reset or readout pulses. Accordingly, these two circuits continue their examination of any train of consecutive error pulses regardless of counting interval duration, and they generate a pulse for triggering amplifier 43 in response to a bit interval which includes an error pulse followed by a bit interval which does not include an error pulse.

Summarizing the operation of the puise distribution indicator described herein, all error pulses occurring duringa given period of time are counted by examining time intervals of predetermined maximum duration including a lirst error pulse. The number of pulses occurring during each such interval is counted in a binary counting system, translated into an equivalent decimal count at the end of the interval, and stored in an appropriate one of a plurality of decimal registers. accomplished by totalling separately the number of counting intervals having diiiercnt total numbers of error pulses. Each counting interval-is timed to have a predetermined maximum duration, but lit may be terminated sooner in response to the counting of a predetermined maximum number of errors or in response to the occurrence of an erroneous bit interval followed by a bit interval which includes no error pulse.

Although this invention has been described in connection with a particular embodiment thereof, it is to be understood that additional embodiments thereof which will be obvious to those skilled in the art are included within the spirit and scope of the appended claims.

What is claimed is:

1. A circuit for registering pulse occurrence patterns in a train of pulses during time intervals of predetermined The storage of decimal counts isduration, each of said time intervals comprising at least one period during which a pulse may or may not occur, said circuit comprising means for counting at least n pulses, said counting means generating a different electric signal for each pulse counted thereby during an interval, means for applying pulses to said counting means, n registers responsive to said different electric signals for totalling interval puise counts, counting interval control means responsive to one of said pulses for generating an output voltage wave having a duration corresponding to said predetermined duration, means connected to the output of said control means for generating a readout pulse in response to the termination of said Wave, coupling means responsive to said readout pulse for applying each of said electrical signals to one only of said n registers thereby separately totalling the numbers of said interval pulse counts of different magnitudes, means responsive to said readout pulse for resetting said counting means to zero, means connected to said counting means for initiating the generation of said readout pulse in response to the counting of a predetermined number of said pulses during one ot said intervals, means for detecting consecutive pulses, and means for connecting the last-mentioned means to said control means for initiating the generation of said readout pulse in response to a pulse followed consecutively by a period in which a pulse does not occur.

2. In a pulse distribution indicator a source of pulses, means for counting the number pulses occunring in counting intervals of controllable duration, means applying said pulses to said counting means, counting interval controlling means responsive initially to the iirst pulse in each of said intervals for generating a readout pulse at the end of each of said intervals, means connecting the output of said pulse source to the input of said controlling means, n count indicating means, means for connecting said count indicating means to said counting means, and means `applying said readout pulse to the last-mentioned connecting means for actuating a different one of said count indicating means for each ditierent total number of pulses counted during said intervals.

3. A random pulse distribution indicator comprising a source of random pulses, means connected to said source for counting said random pulses, a circuit connected to said source and responsive to a first random pulse for controlling the duration of an interval during which said irst pulse and subsequently occurring random pulses are to be counted, said circuit producing a readout pulse in the output thereof upon tbe termination of said interval, n count registers, means responsive to said readout pulse and to pulse counts of different magnitudes in said counting means for actuating diterent ones of said registers, respectively, and means in said actuating means responsive to the counting or" a predetermined number of random pulses for triggering said control circuit to produce said readout pulse.

4. In a random pulse distribution indicator a source of random pulses, means connected to said source for counting the number of said random pulses which occur during separate time intervals, said counting means producing a different electric signal in response to each pulse counted during one of said intervals, a circuit connected to said source and responsive to a iirst random pulse from said source for controlling the duration of said intervals and for producing an output pulse at the termination of each of said intervals, a plurality of count registers, pulse responsive means for coupling each of said different signals to a ditierent one of said registers, respectively, means for applying said output pulse to said coupling means, and means in said circuit for triggering said circuit to generate said output pulse in the absence of consecutive random pulses.

5. A random pulse distribution indicator comprising a source of random pulses, means connected to said source for counting the number of said random pulses occurring during each ot a plurality of time intervals, said counting means comprising a plurality of binary counter stages connected for actuation in sequence to produce a plurality of binary voltage signals representing the binary count of said random pulses, a control circuit connected to said source and responsive to a first one of said random pulses for regulating the duration of said intervals, said control circuit including means for producing an output pulse in response to the termination of each or" said intervals, means connected to said control circuit and responsive to said output pulse for generating a readout pulse, a plurality of decimal registers, a binary-to-decimal translator coupled between said counter stages and said registers, means applying said readout pulse to said translator, and said translator being responsive to said readout pulse and to said binary voltage signals for actuating a different one only of said registers lor ditierent binary count.

6. ln a random pulse distribution indicator, x binary counter stages for counting said pulses, each of said stages comprising a bistable multivibrator liaving one input terminal and two output connections, means for applying random pulses to said input terminals to actuate said counters in sequence in a binary manner thereby producing binary voltage waves of opposite phase in the two loutput connections of each of said stages, n coincidence gates each havinsT x input terminals and one output terminal, n decimal registers, means for connecting each of said gate input terminals to one of said counter output terminals for biasing one only of said gates into coincidence for each different combination of binary conditions of said Voltage Waves, a source of counter readout pulses, and means responsive to the coincidence condition in said one gate and to one of said readout pulses for coupling said one gate to a corresponding one of said registers.

7. The random pulse distribution indicator in accordance with claim 6 in which said coincidence responsive coupling means comprises a source of potential and individual coupling means connected to the output terminal of each of said gates, said individual coupling means comprising iii-st amplitude selecting means for connecting said source of readout pulses to the output terminal of said each gate, said readout pulse source biasing said first amplitude selecting means for conduction in the absence of a readout pulse, second amplitude selecting means for connecting said potential source to the output terminal of said each gate, said second amplitude selecting means being biased for conduction in response to noncoincidence of said each gate or in response to conduction in said iirst amplitude selecting means, said second amplitude selecting means being biased for nonconduction in response to coincidence of said each gate and nonconduction of said iirst amplitude selecting means, third amplitude selecting means for connecting the output terminal of said each gate to its corresponding register, and bias means connected to said second and third amplitude selecting means for basing said third amplitude selecting means into conduction in the absence of `conduction in said second amplitude selecting means.

8. The random pulse ditsribution indicator in accordance with claim 6 in which the nth one of said coincidence gate comprises means for triggering said readout pulse source for producing a readout pulse to actuate said coupling means in response to coincidence in said nth gate.

9. In a random pulse distribution indicator, x binary counter stages for counting the number of random pulses occurring in controllable time intervals, each of said stages comprising a bistable multivibrator having one input terminal and two output connections, means for applying random pulses to said input terminals to actuate said counters in sequence in a binary manner, 2x cathode follower circuits, means for connecting the input of each of said cathode follower circuits to a diterent one of said counter output connections, =11 decimal registers, a binaryto-decimal count translator for coupling the output. of said cathode follower circuits to said decimal registers, said translator comprising 11; coincidence gates having x insnaar/ao put terminals and one output terminal, means for connecting eacb` ol said x input terminals to tbe output of one said cathode follower circuits to bias a different one of said n gates into coincidence in response to escll ditferent binary count thereby producing a voltage output signal in said :one gate, means for connecting each of said gate output terminals to a different one oi said decimal registers, and interval control means connected to said gate output terminals in multiple and responsive to one ot' said random pulses for triggering said one gate at tbe end of each of said intervals to cause said voltage signal to afctuate a corresponding decimal register.

10. The random pulse distribution indicator in accordance with claim 9 which comprises in addition a reset pulse generator, means tor connecting the output of said interval controlling means to the input oi said reset pulse generator for generating 4a reset pulse in response to tbe termination of each of said intervals, and means for applying said reset pulse to said binary counters for resetting said counters to the zero count condition.

11. A random pulse distribution indicator for detecting the occurrence of random pulses in time intervals which comprise recurring time periods, said indicator comprising a source ot random pulses, means connected to said source for counting the random pulses occurring in eacli of said intervals, means for registering tlic random pulse count at t'ne end of each ot said intervals, means responsive to a readout pulse for couplinry said counting means to said registering means, a monostable saw-toot Wave generator having a natural period of oscillation greater than the duration of one of said periods, means for applying random pulses to said saw-tooth generator' for initiating a cycle of oscillation, a bistable multivibrator, means for connecting the output of said sawtooth generator to tbe input of said multivibrator for triggering said multivibrator into a first conducting condition in response to tbe initiation of said cycle and into a second conducting conditon in response to a predetermined portion of tbe saw-tooth wave occurring more than one of said time periods after said initiation, and means responsive to the triggering of said multivibrator into said second condition for applying a readout pulse t said coupling means.

12. ln a random pulse distribution indicator for detecting the occurrence of random pulses in successive time periods making up controllable time intervals, means for generating a control pulse in response to the occurrence of a lirst one of said time periods which includes a random pulse followed consecutively by a second one of said time periods which does not include a random pulse, the last-mentioned means comprising a monostable saw-tooth oscillator having a natural period of oscillation which is greater than tbe duration of one of said periods, means for apply-ing said random pulses to said oscillator for initiating a cycle of oscillation, a bistable multivibrator lraving an input terminal connected to the output of said oscillator for triggering said multivibrator to a first stable condition in response to the initiation of said cycle and to a. second stable condition in response to a subsequent portion of said cycle, and means for deriving said control pulse from said multivibrator in response to the triggering thereof to said second stable condition.

13. A random pulse distribution indicator for detecting the occurrence of random pulses in successive time periods making up controllable time intervals, said indicator comprising means for counting the random pulses occurring in each interval, means for registering the count at the end of each interval in response to a readout pulse, means for controlling the duration of said intervals comprising a first trigger circuit for generating a sharp impulse in response `to the application of a trigger pulse thereto, means for applying said random pulses to said lirst trigger circuit, a second trigger circuit for generating a rectangular pulse in response to said impulse, tire duration of said rectangular pulse corresponding to the duration of one of said intervals, means for applying said impulses to actuate said second trigger circuit, means responsive to said rectangular pulse tor suppressing random pulses in the input to said rst trigger circuit for the duration of said rectangular pulse, means responsive to tlie 'termination of said rectangular pulse for actuating said counting means to readout to said register means, a monostable saw-tooth wave oscillator having a natural period greater than the duration of one of said time periods, means for applying said random pulses to said oscillator for initiating a cycle in said saw-tooth Wave, a bistable multivibrator having an input terminal connected to said oscillator for triggering said multivibrator into a irst one of its stable conditions in response to the initiation of said saw-tooth wave, a predetermined potential level in said saw-tooth wave triggering said multivibrator into a second one of its stable conditions, means for deriving a pulse from said multivibrator in response to the triggering thereof to said second stable condition, and means responsive to the lastmentioned pulse for biasing said second trigger circuit to terminate said rectangular pulse.

14. A circuit for translating the binary representation of a number into tne decimal representation thereof, said circuit comprising a source of 2n binary signal voltage Waves, the combined binary conditions of said Waves at any one time comprising the binary code representation of a number, a plurality of decimal count indicating means and a corresponding plurality of coincidence gates, cach oi said gates having n input connections and one output connection, means connecting said 2n signal voltage Waves to said gate input terminals for biasing a different one only of said gates into coincidence While at tbe same time biasing tire remainder of said gates into noncoincidence in response to each ol said combined binary conditions of said signal voltage Waves, and means for coupling the output of said one gate 'to its corresponding decimal count indicating means.

15. rThe translating circuit in accordance with claim 14 in which said coupling means comprises a source of trigger pulses, a source of potential, and individual coupling means connected to tbe output terminal of each of said gates, said individual coupling means comprising first amplitude selecting means for connecting said source of trigger pulses to tlie output terminal of said each gate, said trigger pulse source biasing said lirst amplitude selecting means for conduction in the absence of a trigger pulse, second amplitude selecting means tor connecting said potential source to the output terminal oi said each gate, said second amplitude selecting means being biased for conduction in response to noncoincidcnce of said each gate or in rcsponse to conduction in said rst amplitude selecting means, said second amplitude selecting means being biased for non conduction in response to coincidence of said each gate and nonconduction of said rst amplitude selecting means, third amplitude selecting means for connecting the output terminal of said each gate to its corresponding decimal count indicating means, and bias means connected to said second and third amplitude selecting means for biasing said third amplitude selecting means into conduction in the absence of conduction in said second amplitude selecting means.

References @lated in the tile oi this patent UNITED STATES PATENTS 

1. A CIRCUIT FOR REGISTERING PULSE OCCURRENCE PATTERNS IN A TRAIN OF PULSES DURING TIME INTERVALS OF PREDETERMINED DURATION, EACH OF SAID TIME INTERVALS COMPRISING AT LEAST ONE PERIOD DURING WHICH A PULSE MAY OR MAY NOT OCCUR, SAID CIRCUIT COMPRISING MEANS FOR COUNTING AT LEAST N PULSES, SAID COUNTING MEANS GENERATING A DIFFERENT ELECTRIC SIGNAL FOR EACH PULSE COUNTED THEREBY DURING AN INTERVAL, MEANS FOR APPLYING PULSES TO SAID COUNTING MEANS, N REGISTERS RESPONSIVE TO SAID DIFFERENT ELECTRIC SIGNALS FOR TOTALLING INTERVAL PULSE COUNTS, COUNTING INTERVAL CONTROL MEANS RESPONSIVE TO ONE OF SAID PULSES FOR GENERATING AN OUTPUT VOLTAGE WAVE HAVING A DURATION CORRESPONDING TO SAID PREDETERMINED DURATION, MEANS CONNECTED TO THE OUTPUT OF SAID CONTROL MEANS FOR GENERATING A READOUT PULSE IN RESPONSE TO THE TERMINATION OF SAID WAVE, COUPLING MEANS RESPONSIVE TO SAID READOUT PULSE FOR APPLYING EACH OF SAID ELECTRICAL SIGNALS TO ONE ONLY OF SAID N REGISTERS THEREBY SEPARATELY TOTALLING THE NUMBERS OF SAID INTERVAL PULSE COUNTS OF DIFFERENT MAGNITUDES, MEANS RESPONSIVE TO SAID READOUT PULSE FOR RESETTING SAID COUNTING MEANS TO ZERO, MEANS CONNECTED TO SAID COUNTING MEANS FOR INITIATING THE GENERATION OF SAID READOUT PULSE IN RESPONSE TO THE COUNTING OF A PREDETERMINED NUMBER OF SAID PULSES DURING ONE OF SAID INTERVALS, MEANS FOR DETECTING CONSECUTIVE PULSES, AND MEANS FOR CONNECTING THE LAST-MENTIONED MEANS TO SAID CONTROL MEANS FOR INITIATING THE GENERATION OF SAID READOUT PULSE IN RESPONSE TO A PULSE FOLLOWED CONSECUTIVELY BY A PERIOD IN WHICH A PULSE DOES NOT OCCUR. 